Hull construction of submarine boats.



L. Y. SPEAR; HULL CONSTRUCTION OF SUBMARINE BOATS.

APPILICATION men MAR. 13 1911. RENEWED FEB. 22, ms.

PatentedSepfi. 21, 1915.

9 SHEETS-SHEET INVENTOR ATTORNEYS L. Y. SPEAR. HULL CONSTRUCTION OF SUBMARINE BOATS.

APPLICATION FILED MAR. 13,191. RENEWED FEB. 27,1915.

Patented Sept. 21, 191.5.

9 SHEITS-SHEET 2 Patented Sept. 21, 1915.

9 SHEETSSHEET 3.

llill lifllll JT' lNVENTOR w y m W/ ATTORNEY) PatentedSept. 21, 1915.

9 SHEETS-SHEET 4.

& m 3% W ATTORNEYS L. Y. SPEAR. HULL CONSTRUCTION OF SUBMARINE BOATS.

APPLICATION FILED MAR. 13. l9l1- RENEWED FEB. 27, I915- Patented Sept. 21, 1915.

9 SHEETS-SHEET 5 INVENTDR WITNESSES L. Y. SPEAR.

HULL CONSTRUCTION OF SUBMARINE BOATS.

APPLICATION FILED MAR. 13. I9. RENEWED FEB. 21. 1915.

l ,1 54,21 5. Patented Sept. 21, 1915.

9 SHEETS-SHEET 6.

E5 WITNESSES: H lNVENTOR L. Y. SPEAR.

HULL CONSTRUCTION OF SUBMARI'NE BOATS.

APPLICATION FILED MAR. 13. I9Il.

RENEWED FEB-2711915.

Patented Sept. 21, 1915;

9 SHEETS-SHEET 7.

llll' INVENTOR ATTORNE YQ L. SPEAR. HULL CONSTRUCTION OF S UBMARINE BOATS. APPLICATION FILED MAR. 13. l91l.\RENEWED FEB. 27. I915.

Patented Sept. 21, 1915.

9 SHEETS-SHEET 8.

WITNESSES:

L. Y. SPEAR.

HULL CONSTRUCTION OF SUBMARTNE BOATS.

APPLICATION FILED MAR. 13. E911.

RENEWED FEB. 27.1915.

Patented Sept. 21, 1915.

ATTORNEYS 9 SHEETS-SHEET 9. 1 z

STATES PATENT @FFKCR LAWRENCE Y. SPEAK. OF QUINCY. MASSACHUSETTS, ASSIGNOR-iTO ELECTRIC BOAT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

HULL CONSTRUCTION OF SUBMARINE BOATS.

Specification of Letters Patent.

Patented Sept. 21, 1915.

Application filed March 13, 1911, Serial No. 614,067. Renewed Fe hruary 27, 1915. Serial No. 11,070.

To all 11:71 (Hit it m (13 concern .7

lie it known that l. LAWRENCE Y. SPEAK, a citizen of the United States, residing at Quincy, county of Norfolk, State of Massachusetts. have invented certain new and useful Improvements in Hull Construction of Submarine Boats; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The primary objects of the invention are to provide a submersible vessel having a. comparatively light structure capable of withstanding the external pressure resultant from deep submergence and which will admit of comparatively light surface draft with adequate stability on the surface and submerged and ample head room throughout the interior portions occupied by the crew in handling the vessel, and to simplify and improve the handling of the vessel by .certain constructions and arrangements of the tank coi'npartments hereinafter more fullv set forth.

To this end the vessel is made up of an inner hull containing only those parts of the boat which are necessarily subjected to the pressure of leep subn'iergence, which inner hull is made of such shape in cross section as to lend itself to a structure capable of re sisting the greatest pressure to which it will be subjected in such sulunergeiiire: and an outer hull of light construction not adapted to withstand the pressure of deep submergence and merging into the lines of the inner hull so as to complete the contour of the boat. The boat is equipped with a number of submergence tanks, including the main ballast tanks (preferal'ily divided into forward, middle and after main ballast tanks) forward and after trimming tanks, an auxiliary ballast tank, and preferably an adjusting tank. The empty main ballast tanks supply a large element of buoyancy to the vessel running light, and, upon being filled, suoply a large elementof weight when the vessel is submerged: and they am so related in volume to the reu'iainder ofthe vessel that when the main ballast tanks are full the vessel is nearly awash. During submergence these tanks are open to the seaand completi-tly filled with water. and are not subjected to the pressure of submergence. In accordance with my invention they are 10 practicable center of gravity.

cated in the light outerhull. \Vhen it is desired to secure maximum stability submerged the boat should be designed with these tanks as low as possible on the contour of the vessel in order to give it the lowest If, on the other hand, more stability on the surface is desired at the expense of submerged stability, the design will be such that the tanks are virtually raised or their shape altered so as to increase the area of the waterplane of flotation in the surface condition. WVhen a minimum surface draft is required, these main ballast tanks, or that'portion of them in wake of the inner hull, are made of broad beam and of minimum vertical height. The trimming tanks, on the other hand, are employed for the purpose of bringing the vessel to aneven keel before submergence, and in practice are seldom or never completel y tilled, so that they must be capable of withstanding the pressure of. deep submergence. The auxiliary ballast tank is employed for the purpose of overcoming such portion of the reserve buoyancy'of the vessel as may be desired after the main ballast tanks are completely filled and the vessel is properly trimmed fore and aft by the trimming tanks. In practice this tank is seldom or never completely full. and it must therefore be capable of withstanding the exterior pressure due to deep subn'iergence. The adjusting tank. if fitted, is equipped with a mechanism for accurately measuring the quantity of water admitted to and discharged from it. It is employed for the purpose set forth in U. S. Patents Nos. 772,970. dated October 25, 1904, and 805,496, dated November 28, 1905. This tank also is not necessarily full when submerged, and must therefore either be an internal tank or capable of withstanding the exterioi pressure due to deep submergence. The trimming tanks are, in accordance with my invantion, made a part of the strong inner hull, and in order to have the maximum effect for their intended purpose, are located at the. extreme forward and aft portions thm'eof. The auxiliary ballast tank is likewisemade a part of the inner hull, and should be so constructed and located, whether made of one or a plurality of compartments, that the center of gravity of its contents is in or near a vertical line passing through the center of gravity of the vessel submerged, so that the amount of Water in it has little or no influence on the fore and after trim of the vessel. It is desirable, also, to arrange the design so that the same vertical line passes through or very near to the center of volume of emergence when the main ballast tanks are full and the vessel has been brought to an even keel, so that when the vessel is lowered in the water by filling the auxilia v tank, it will go down without disturbance of trim.

Many of the features of-my invention are applicable to vessels of widely different configuration, as will be understood, but for the purpose of producing a boat with fine lines at the bow, and adapted for high speed, I have employed a construction having a stem. portion of somewhat similar shape to an ordinary ship, that is, of considerable height in comparison to its. width, and preferably merging into the.torpedo tube shutters which complete the extreme forward end of the vessel. Such a hull construction does not lend itself. to the resistance of great pressure, and I overcome this vdifficulty by making this high narrow portion of the hull a part of the light outer hull construction and using it as the forward main ballast tank. These main features of ,my invention, as well as. important and novel details thereof, will. best be understood from a consideration of the following description ofthe preferred form, reference being bad to the accompanyingdrawings. in which: i i 1 Figure 1, represents a side elevation showing the outer bull in. section. Fig. 2 repre sents a bottom view also showing the outer bull in section. Figs. 3, 4 and 5, represent on a larger scale bow, midship and stern portions respectively, in vertical section taken onthe keel line. Figs. 6, 7 and 8, represent bow, midship and-stern portions respectively in horizontal section through the center line of the vessel. Figs. 9, 10 and 11 represent vertical cross sections taken at lines 9-9, 1019, and 1l11, respectively of Fig. 3 in the (Llirectionof the arrows. Figs. 12 and 13 represent vertical cross sections taken at lines 12- 12 and 1$-13 respectively of'Fig. l in the direction of the arrows. Figs. 14, 15 and 16 represent vertical cross-sections taken at lines 1414-, 1515, and 16 1( of Fig. 5 in the direction of the arrows. Fig. 17 represents a like view to Fig. 12 of a modified construction.

Referring to the drawings, the. inner bull or strong hull 2, shown. complete in Figs. 1

and 2, does not extend entirely to the how,

but is there completed by a compartment 3.

This division of the hull of the vessel, if

shaped to facilitate its progress through the water, as suggested above, is not well adapted to withstand exterior pressure equal to that encountered during deep submergence;

bulkhead the front wall of the strong hull 2. Torpedo tubes 6. 6 extend throli-gh bulkhead and two other bulkheads 7. 7. in the rear of bulkhead 5, whereby bulkhead 5 is consid erably stiffened.

The space between the bulkheads 7 con stitutes the for 'ard trimming tank 28, and the space between forward bulkhead 7 and constitutes the torpedo compensating tank. I

It will be seen, by referring to Figs. 9, 19 and 11 and their position on Fig. 3, that the forwardpart of the strong hull 2 is slightly elliptical with its major axis vertical, and is well adapted for exterior pressureresisting construction. From this form it gradually merges into a tube circle as showu-in Fig. 10 and then into an ellipse with its major axis horizontal at bulkhead 8, see Fig. 5, and from this point its outer surface is continued as outer hull 19 and the strong hull 2 is'inclosed within it. The strong hull 2 is in greater part cylimlrical, but embraces at its lower portion a box like rectangular structure 19, which forms part of the pressure resisting hull and accommodates the storage battery equipment :20, the adjusting tank 21. and the auxiliary ballast tank 22 at a low and convenient level. i 'lhroughout this central sectionof the boat. the'strong hull 2 is stitl'eu cd by flanged cradle plates or braces 23 between it and the outer hull 18. and this bracing is prin' cipally applied to the box-like portion l9,'

and its junction with the cylindrical por.

translating devices necessar the opera-- tion of the boat maybe used in this way but the engine frames alone are so employed in the particular embodiment of the invention illustrated.

It will be understood that the particular form of inner and outer hull illustrated and just above described represents merely the preferred embodiment of the invention and that it is not essential to the invention that true elliptical contours be used. ()n the con trary these may be departed from to any extent desired, providing the section of'single strong hullis of a form capable of being sufficiently reinforced to withstand deep submergence pressures. Ina like manner, the main portion of the section of strong hull amidships, which is here shown as circular, in cross section, except where the rectangular tank breaks into it, need not necessarily be an exact circle, although that is the preferred form, giving the maximum strength with the minimum weight.

The portion of the strong hull just forward of the bulkhead 25 is divided off by a second complete transverse bulkhead, to form the after trimming tank 29, as shown in Figs. 5 and S.

From bulkhead to the stern of the es sel I may conveniently employ a structure supporting the twin propellers and which, proceeding from the ellipse with horizontal major axis at bulkhead 25, as shown in Fig. 16, merges through gradually flattening elliptical sections into a spectacle frame stern post, as illustrated in the accompanying drawings and'fully described in my lnited States Patent No. 878,752 of February 11, 1908, and when such construction is, used I leave the portion aft of bulkhead open to the sea, and use it as a fuel tank if desired, in accordance with the disclosure ofv that patent. It will. be understood, however, that this particular construction of stern forms no part of the present invention and the stern may be differmtly constructed to suit the requirements of any particular design. For example, if stern torpedoes are-to be used the axis line of this stern section -will be inclined or curved up. and the propeller shafts passed through stuffing boxes and supported by struts in the ordinary way. Or if the construction of stern according to Patent No. $78,752 is not desired, the strong hull construction may be carried so far aft as is consistent with the form and capable of being suitably reinforced to withstand deep submergence pressures. rib-aftof such point, the stern construction would be similar to the how but would be flooded and open to the sea when the vessel is submerged.

From the description it will be understood that in the preferred form-illustrated the hull of the vessel is made up of the following sections: The extreme bow is a portion of the weak outer hull, and is used as forward main ballast tank, back at least to a point where the hull section is of such shape as to lend itself to a structure capable of resisting the pressure due-to deep submergence. Then follows a section'of single hull which passes from a forward portion of which the cross section is an ellipse with its major axis vertical, through a circular portion, into an after portion of which the cross section is an ellipse with its major axis horizontal. Then follows the midship section which is of double hull construtcion. The inner strong hull is generally circular in. cross section, but is interrupted at the bottom to embrace the box-like portion 19. It will be observed that the inner strong hull midship section, which constitutes a substantial portion of the buoyancy of the vessel when submerged, has the center line of its volume located substantially above the center line of the volume of the forward and aft strong hullsec tions, and by virtue of this location adds to the stability of the vessel when it is running under water. It is, furthermore, of advantage to have this midship cylindrical section of strong hull extend above the single hull sections forward and aft of it, since thereby the emerging portion of the hull, when the ballast tanks are full, is quite symmetrical, so that the center of volume of emergence follows a straight vertical line, as the vessel is submerged. The space be: tween the inner and outer hull of this double hull portion constitutes the main ballast tanks, and their volume is so related to the design of the vessel that when the main ballast tanks are filled, and the vessel is properly trimmed, the only portion of the hull out of water will be the upper part of the cylindrical inner hull section 2. The auxiliary ballast tank'22 is located at approximately the center of this double hull section, so that the center of gravity of its contents is in substantially the same vertical line with the center of volume of emergence when the main ballast tanks are filled, and when the auxiliary ballast tank, which is the last tank to be filled, is flooded, the vessel sinks in. the water without appreciable disturbance of trim. Then aft of the double hull structure is a strong section of single hull. construction, stiffened as may be necessary to suit conditions, the stiffening being obtained in the preferred construction, by the use of the frames of the translating devices as girders. The extreme tail is in the shape of a flat ellipse merging into a spectacle f 'ame constituting the stern post, and is preferably non-pressure resistin and may be left freely open to the water or used as a fuel storage tank, asexplained.

The embraced lower box-like portion 15) of the midship section of strong hull contains the storage battery. In the particular embodiment shown the storage battery is divided into two parts, separated amidships' by a midship well, though it is possible, and sometimes convenient. to locate all of the battery forward of the midship well. At the midship well, within the strong hull, are

-the adjusting tank tank,

case, the flooding valve openings located the auxiliary tank 22, and within it 21, which is a structural formed by partitioning off the central portion of structure 19 as shown in Figs. 4 and 12. v

The space 30, between the tion of strong hull 2 and the which is used as main ballast midship secouter hull 18, tankage, may

be divided as desired. In the present in-.

stance it is shown divided at approximately the center of the boat by bulkhead 70, to form the after main ballast tank7l and the middle main ballast tank72. It will be observed that this tankage as illustrated is low down on the hull so as to be well submerged whenever the vessel is carrying water ballast. For the purpose of giving light surface draft this portion of the hull is, as shown, spread out broadly toward the bottom, which is nearly fiat, and is of small height as compared With its Width. This arran ement is well ada )ted to the combination of light surface draft with a. large submerged stability.

A siuwrstructure inclosing space 31 is built throughout the entire length of the stability and a good surface boat and servesto reinforce all of the .be-.

fore-mentioned sections, as well as to form a deck for the vessel. This superstructure is ordinarily non-water tlght, and is pro- -vided with vents, and. with scupper holes whereit'joins the hull. to render it self-bailing and self-filling. In the modified construction, shown in cross section, in Fig. 17,

however, the midship outer hull section 18,

. instead ofmerging into the cylindrical midship section of the strong hull 2, is continued up outside thereof to' form a midship superstructure section, .which is divided from the main ballast tank, near the water line, by partitions 32. This midship superstructure section' may be provided with flooding valves, as a supplemental ballast tank. In such, should be Just above partitions 32, so that this portion of the superstriuztlue will still be self-bailing and self-filling'when the valves are left open.

Closures for sea inlets and air and pump connections are provided for all of the nonpressure resisting spaces which are intended for use as ballast tanks, the ballast tank space 30 in the middle section, the bow and stern tanks 3 and 4, and the superstructure space if it is made watertight, and they may be flooded or exhausted at will either singly or in combinations'at such depths as their structure will permit.

it will-be readily seen that the structural features described allow' of an extremely strong and compact construction and arrangement with a minimum weight of ma- 'terial and it is thought that the following .trimmed fore and aft, as desired. by

trimmed condition by ing of the superstructure.

and vents, so as to be used description of operation will best illustrate the cooperationof the several features of the I be reduced to a comparatively small amount.

To effect this, the superstructure valves (if a tight superstructure is fitted) are opened and the main ballast tanks filled. The ressel then settles low in the water and is the admission ofsuitable quantities of water into one or both of the trimming tanks 28 and 29. After this is done. the only remaining buoyancy is that residing in the conning tower and in the upper portion of the midship strong hull section. So much of this remaining buoyancy as is desired is destroyed by admitting water to the auxiliary tank within the strong hull, the balance of the superstructure space filling as the vessel sinks. If an adjusting tank is fitted, final adj ustment'may be accomplished by its normal operation. Owing to the construction above described, the final operation of trimnnng is effected without any material change in the fore and aft trim of the vessel.

It is obvious that when a tight superstructureis fitted, additional buoyancy and stability may be obtained in a partially The wide variation of.water displacement between the floating and submerged conditions of a vessel embodying the features of this invention and the small area exposed to pressure during the submergence permit of the'construction' of an etlicient light or moderate draft submarine boat. 1'

Itis obvious that various changes may be niade in the details of construction and arrangement without departing from the spirit of this invention.

I do not claim herein broadly-the RI? rangement by which the main ballast tanks are so related in volume to the vessel as to leave only the symmetrical upper portion of the midship section of the strong hull out of water when the main ballast tanks are flooded, together with an auxiliary tank having the center of gravity of its contents on or near the vertical line passing through the center of volume of emergence, because this projecting portion of the hull constitutes the synnnetrical buoyant protuberance postponing the floodis not required to 1 ship section,

weak hull.

with water when the boat is deeply submerged, and which therefore would have to withstand the pressure of deep submergence, a strong tank.

What I claim is:

l. A hull construction for submarine boats, comprising a double hulled midship section consisting of an inner strong hull and an outer weak hull, and single strong hull sections forward and aft of said midthe center line of the volume of hull of the midship section lying above the center line of the volume of the forward and aft strong hull sections, said single strong hull sections forming continuations of the weak hull of said midship section; substantially as described.

2. A hull construction for submarine boats, comprising a double hulled midship section consisting of an inner strong hull and an outer weak hull, single strong hull sections forward and aft of said midship section, the center line of the volume of the inner strong hull of the midship section lying above the center line of the volume of the forward and aft strong hull sections, and the the inner strong upper contour of the strong hull midship section rising above the upper contours of the forward and aft sections, said single strong hull sections forming continuations of the weak hull of said midship section; substantially as described.

3. A submersible boat comprising an inner hull in greater part approximately cylindrical but having a rectangular under portion embraced by the cylindrical portion, an outer hull, and bracing between said inner and outer hulls uniting both hulls to render said inner hull resistant to exterior pressure.

4. In a submersible boat, a double hull section comprising a strong hull, a weak hull surrounding said strong hull, completing the contour of said section and providing an inter-hull space below and at the sides of said strong hull for use as ballast tanks which are completely filled with water during deep submergence, and a strong tank located in and occupying a portion of said inter-hull space; substantially as described.

5. A submersible boat comprising a strong hull designed to withstand the pressure of ,deep submergence, a weak hull afiording main ballast tanks without said strong hull, and a superstructure open to 'the sea built upon. said strong hull and separated from said main ballast tanks.

6. A submersible boat havinga double hull midship section, the inter-hull area constituting main ballast tanks, the inner hull being substantially cylindrical to give great strength, and the outer hull being hung low on the inner hull and flaring outwardly to give a shallow draft when empty and a low I have also termed a tank which is not necessarily completely filled center of gravity and great meta-centric height when filled.

l. A submersible boat having a strong hull comprising a forward portion merging from a generally elliptical cross-section with its major aXis vertical at the forward end of the section, into a generally elliptical crosssection with its major axis horizontal at the after end of the section, a substantially cylindrical central section, and an after section the cross-section of which is generally elliptical with its major axis horizontal, in combination with an outer hull portion surrounding the central section of the strong hull and completing an unbroken contour with the forward and after sections thereof.

8. A submersible boat having a strong hull comprising a forward section merging from a generally elliptical cross-section with its major axis vertical at the forward end of the section into a generally elliptical crosssection with its major axis horizontal at the after end of the section, a substantially cylindrical central section, and an-after section the cross-section of which is generally elliptical with its major axis horizontal, in combination with an outer hull portion surrounding the central section of the strong hull and completing an unbroken contour with the forward and after sections thereof and a high narrow bow section of weak hull constituting a ballast tank and merging into the forward end of the forward strong hull section.

9. A submersible boat having a strong hull comprising a forward section merging from a generally elliptical cross-section with its major axis vertical at the forward end of the section into a generally elliptical cross; section with its major axis horizontal at the after end of the section, a'substantially cylindrical central section, and an after section. the cross-section of which is generally elliptical with its major axis horizontal, in combination with an outer hull portion surrounding the central section of the strong hull and completing an unbroken contour with the forward and after sections thereof, said central section being raised above the forward and after sections to constitute a symmetrical buoyant protuberance amidship. I

10. A submersible boat having a high narrow bow, the bow section being incapable of withstanding the pressure of deep submergence back at least to a point where the shape of the hull lends itself to a structure capable of withstanding such pressure, said weak bow section constituting a part of the water ballast system of the boat, a forward strong section of single hull into which the said how section merges and which is suitably stifiened to withstand the pressure of deep submergence, a midship section of double hull construction, the space between the tion of double hull r-onstructimi,

"between the hulls row bow. the bow section being incapable of,

withstanding the pressure of deep submergeuce back at least to a point where the shape i of the hull lends itself to a structure capable of withstanding such pressure, said weak bow section constituting a part of the water ballast system of the boat, aforward strong section of single hull into which the said bow section merges and which is suitably stiffened. to withstand the pressure of dee subi'nergence, a midship section of double hull construction, the space between the hulls constituting portions of the water ballast system of the boat, and an after strong section of single hull suitably stiffened to r'esis'tthe pressure of deep submergence, the central double hull section being made u of an innerhull shaped to withstand the pressure of deep submergence and an outer hull completing the unbroken contour of the vessel amidship and not adapted to with stand the pressure of deep submergence.

12. A submersible boat having a high narrow bow, the bow section being incapable of withstanding the pressure of deep submergence back at least to a point where the shape of the hull lends itself to a structure capable of withstanding such pressure, said weak bow section constituting a part of the water section or" single hull into which the said how section merges and which is suitably stifi'ened to withstand the pressure of deep submergence a midship section of double hull construction, the 'space between the hulls constituting portions of the water ballast system of the tion of single'hull ballast svstem of the boat,'-a forward strong suitably stiffened to re sist the pressure of deep submergence, and a final stern. section incapable of withstanding such pressure but-open to the water of submergence to enable it to "resist-such pressure.

13. A submersible boat having a high narrow how, the bow section being incapae ble ofwithstanding the pressure of deep sulnnergence back at least to a point where the shape of the hull lends itself to a struc-' ture capableof withstanding such pressure,

said weak bow section constituting a part of the water ballast system of the boat, a forward strong section of single hull into which the said how section merges and which is suitably stiflened to withstand the pressure of deep submergence, a middle secthe space constituting portions of the water ballasbsystem of the boat, an after strong SOClJlOIIJOf single hull suitably stiff boat, an. after strong secened to resist the pressure of deep sub- 'mer,gence and a final stern section incapable broken contour and not adapted to withstand the pressure of deep submergence.

ll. A hull construction for submarine boats, comprisinga double hulled midship hull section consisting of an inner strong and an outer weak hull, and single strong hull sections forward and aft of said midship section, said single strong hull sections forming continuations of the weak hull of said midship section; substantially as described.

15. A hull construction for submarine boats, comprising a double hulled midship section consisting of an inner strong hull and an outer weak hull, single strong hull- I O sections tor-ward and aft of said midship section, said single strong hull sect-ions forming continuations of the'weak hull of said midship section, and. bow and stern single weak hull sections formingcontinuations of said single strong hull sections; substantially as described. 1

16. A submersible boat having a strong hull, comprising a bow section having at its forward end a generally elliptical cross-section with its major axis vertical, a substantially cylindrical section, and an after section the cross-section of which is generally elliptical with its major axis horizontal, in combination with an outer hull portion surrounding the centralsection of the strong .hull and completing an unbroken contour with the forward and after sectionsthereof.

17. A submersible boat having a strong hull, comprising a bow section having at its forward end a generally elliptical cross-section with its major axis tially cylindrical central section, and an after section the cross-section of which is generally elliptical with its major axis hori zontal, in combination with 'an outer hull portion surrounding the central section of the strong hull and completing an unbroken contour with the forward and after sections thereof, and a high, narrow bow section of weak hull constituting a ballast tank and merging into the forward end of the bow strong hull section.

18. A submersible boat having a strong hull, comprising a bow section having at its forward end a generally elliptical crosssection with itsmajor axis verticaLa substantially cylindrical central section, and an after section the cross-section of which is generally elliptical with its major axis horizontal, .in combination with an outer hull use; 15 7 portion surrounding the central section of the strong hull and completlng an unbroken contour with the forward and after sections u lnidship.

In testimony whereof I afiix my signature, 1n presence of two wltnesses.

LAWRENCE Y. SPEAR.

Vitnesses:

F. L. BRAKE, J. E. FITZGERALD, Jr.

Gnpies of this patent may be abta ined for five cents each, by addressing the Commissioner of Ratnts,

Washington, I). 0. 

